This JIP is designed to develop a basin-wide EOS model, and/or formation-specific EOS models for the Powder River. Industry participants will contribute with a participation fee and PVT laboratory reports. The resulting EOS model(s) will provide a means to generate key PVT data for individual wells based on readily-available data such as reservoir temperature, separator gas composition (gravity), crude API gravity, and producing gas-oil ratio. The EOS model(s) can also be used for advanced PVT applications such as black-oil PVT tables needed for reserve calculations, numerical simulation of well performance, and lumped-EOS models that can be used in compositional reservoir simulation of gas-based EOR processes. The technology of developing a single, common EOS model for multiple reservoirs and basins has been developed and used by whitson, formerly known as PERA, for the past 30 years around the world, and most recently for the Eagle Ford, Bakken and Montney basins. This is achieved by including a wide range of fluid samples with measured PVT data (low-GOR to high-GOR) from a basin, multiple reservoirs and groups of formations.